[PATCH 0/1] Fixes for LP:#1494350

[Liang Chen]

This will not be submitted as a upstream stable patch. So I have added
Linux (Ubuntu)
as an affected project to the bug report, and requested help from ubuntu
core dev
team to nominate those release - trusty/utopic/vivid/wily. The impact and
test case
sections are also added to the bug report with the testing feedback of
patched trusty
kernel.

Thanks,
Liang

On Tue, Mar 8, 2016 at 10:21 PM, Stefan Bader <stefan.bader at canonical.com>
wrote:

> On 08.03.2016 14:38, liang.chen at canonical.com wrote:
> > BugLink: http://bugs.launchpad.net/bugs/1494350
>
> Will this not be submitted as a upstream stable patch? If not at least the
> bug
> report should have a Linux (Ubuntu) and tasks for the releases, plus some
> testing feedback with at least one release and that patch added. (imo)
>
> -Stefan
>
> >
> > [Impact]
> > Steal time can get overflowed after loading/migrating of a VM, which
> causes
> > some guest OS like Debian Jessie to extremely large values for steal
> time.
> >
> > % cat /proc/stat
> > cpu 2400 0 1842 650879168 2579640 0 25 136562317270 0 0
> > cpu0 1366 0 1028 161392988 1238598 0 11 383803090749 0 0
> > cpu1 294 0 240 162582008 639105 0 8 39686436048 0 0
> > cpu2 406 0 338 163331066 383867 0 4 333994238765 0 0
> > cpu3 332 0 235 163573105 318069 0 1 1223752959076 0 0
> >
> > [Justification]
> > It is very important for guest system to know the real steal time in
> > virtualized environment. People heavily depend on this figure when
> analysing
> > performance issues in guest system.
> >
> > [Test Case]
> > 1.launching a VM and take down the steal time, e.g. rdmsr 0x4b564d03 to
> read
> >   the location of the steal_time structure in guest and xp /ug
> <location> in
> >   qemu monitor to dump the steal_time value
> > 2.save the state of the VM in a snapshot (savevm)
> > 3.put some stress on the host machine, e.g. stress -c XXX
> > 4.load the state of the VM (loadvm)
> > 5.Look at the steal time again, it will very likely go backwards because
> of
> >   the overflow
> >
> > Marcelo Tosatti (1):
> >   KVM: x86: move steal time initialization to vcpu entry time
> >
> >  arch/x86/kvm/x86.c | 9 ++-------
> >  1 file changed, 2 insertions(+), 7 deletions(-)
> >
>
>
>
> --
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>
>
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